Access to Ultra-High-Molecular Weight Poly(ethylene) and Activity Boost in the Presence of Cyclopentene With Group 4 Bis-Amido Complexes

作者：Narayana Gurram Venkata; Xu Guangjuan; Wang Dongren; Frey Wolfgang; Buchmeiser Michael R^*

来源：ChemPlusChem, 2014, 79(1): 151-162.

DOI：10.1002/cplu.201300378

Zr(IV)complexes of the type [Me2Si{(NR)(6-{2-(diethylboryl)phenyl} pyridyl-2-yl-N)} ZrCl2.thf] (R= tBu (4), adamantyl (7a); thf = tetrahydrofuran), [Me2Si{(NAd)(6-{2-(diphenylboryl) phenyl}pyridyl- 2-yl-N)}ZrCl2](Ad= adamantyl (7b)), the nonbridged half-titanocene complexes of the type [(N-{6-(2-diethylborylphenyl)pyrid-2-yl}-NR) Cp%26apos;TiCl2] (R= Me, Cp%26apos; = C5H5 (12), Cp%26apos; = C5Me5 (13)), and the titanium(IV)-based metallocene-type complex [bis{N( 6-{2-(diethylboryl) phenyl} pyrid-2-yl) NMe}TiCl2] (14) have been synthesized. The structures of complexes 7b, 12, and 13 were determined by single-crystal X-ray diffraction analysis. In solution, complex 4 slowly rearranges to [Me2Si{(N-tBu)(6-{2-(diethylboryl) phenyl} pyridyl-2-yl-N)}(2)Zr] (4a), the structure of which was unambiguously confirmed by single-crystal X-ray crystallography. Similarly, reaction of HfCl4 with Me2Si({RNLi}{6-[2-(diethylboryl)phenyl] pyridyl-2-ylNLi}) yielded the corresponding HfIV complexes [Me2Si{(NR)(6-{2-(diethylboryl) phenyl} pyridyl-2ylN)} 2Hf] (R= tBu (8) and Ad (9)). Upon activation of these complexes with methylalumoxane (MAO), complexes 4, 7a, 7b, and 12-14 showed activities up to 750 kg of polyethylene (PE)/mol(cat). barh in the homopolymerization of ethylene (E), producing mainly linear PE (high-density PE, HDPE) with molecular weights in the range of 1800 000 %26lt; M-n %26lt; 4 x 10(6) gmol(-1). In the copolymerization of E with cyclopentene (CPE), the polymerization activities of complexes 4, 7a, and 7b can be enhanced by a factor of 140 up to 7500 kgPE/mol(cat). bar h, which produced PE-co-poly(CPE) containing 3.5 mol% of CPE. This dramatic increase in polymerization activity for E in the presence of CPE can be attributed to an involvement of CPE in the polymerization process rather than to solvent polarity.

• 出版日期2014-1